Re: canvas colormaps

Trent Piepho (
Thu, 16 Jan 1997 12:53:42 -0800 (PST)

To subscribers of the xforms list from Trent Piepho <> :

On Thu, 16 Jan 1997, Steve Lamont wrote:
> To subscribers of the xforms list from (Steve Lamont) :
> > In other words, works as "advertised." Hmmmmm... I'm on my way into
> > my lab where I've still got 0.81 installed. We'll see what happens...
> I've now tested the colormap swapping problem code on SGIs running 6.2
> and 5.3 and Suns running 4.1.3 and 4.1.4 with XForms 0.81. It runs
> fine on the SGI (colormap swaps as expected) but not on the Suns. The
> Suns are running X11R5 -- the SGIs are running X11R6.

I think I've figured it out. It's a window manager problem. Since fvwm is
derived from twm, it possible that they would have the same bug.

The problem is in how the wm handles the COLORMAP_WINDOWS property. It will
work ok for machines in which the minimum number of colormaps that can be
installed concurrently is the equal to or less than the number of
colormap_windows. The reason is that when the top-level window is entered
the window manaders installs _ALL_ colormaps for windows listed in that windows
colormap_windows property. On an SGI they _all_ get installed and stay
installed, so the window is happy. On lesser graphics hardware only the
last colormap stays installed.

The bug with xforms is that calling fl_set_canvas_colormap doesn't call
XSetWMColormapWindows unless it is called _before_ fl_show_form. However
it's quite possible to change colormaps after the form is shown, and if the
colormap is different than the top level window XSetWMColormapWindows needs
to be called to let the window manager know.

I think I'll take this to the fvwm mailing list. I'm not sure what the proper
thing to do it. xmag does work on fvwm, but I haven't figured out what it's
doing yet. Maybe I'm not reading the X manual correctly, and something more
needs to be done that xforms doesn't do.

|Gazing up to the breeze of the heavens \ on a quest, meaning, reason |
|came to be, how it begun \ all alone in the family of the sun |
|curiosity teasing everyone \ on our home, third stone from the sun. |
|Trent Piepho ( -- Metallica |